LONG DISTANCE CABLE CIRCUIT 



:)/ 



shows the attenuation at average temperature plotted as a function 

 of frequency, while Fig. 5 shows the line impedance. 



Figure 6 shows how the cable circuit attenuation varies with tem- 

 perature at different frequencies. As will be seen from the curves, 

 temperature change produces effects not only in the series losses but 

 also in the shunt losses. The series losses are changed largely because 



10 



30 50 



100 200 500 1000 2000 5000 8000 



CYCLES PER SECOND 

 Fig. 5 — Mid-coil characteristic impedance for 16-ga. B-22 cable pairs at 55° F. 



the resistance of the copper cable conductors changes with tempera- 

 ture, and to a smaller degree because of changes in effective resistance 

 of the loading coils. The shunt losses change with temperature due 

 largely to changes in the conductance losses and, to a lesser extent, 

 changes in the cable capacity with temperature. The conductance 

 loss is approximately directly proportional to frequency so that it 

 has maximum effect at the highest frequency. The effect of temper- 

 ature on the conductance loss is opposite to the effect of tempera- 

 ture on the series loss so that increase of temperature reduces the 

 shunt loss. 



The matter of securing the necessary electrical separation between 

 the 16-gauge program transmission circuits and the other circuits 

 contained within the same lead sheath involved particular study. 

 The use of shielded pairs was considered. Such use of shields, how- 



